New 3.7V Li ion Battery Replacement 330mAh for iPod Nano 2 2G 2nd Gen MP3 with Tools|Mobile Phone Batteries| - AliExpress
iPod Nano 2nd Generation Repair - iFixit
Replacement iPod Nano 2nd Generation Battery 400mAh 616-0282 A1199 Fast Post | eBay
Replaced the dead battery in an old iPod Nano I bought (really wanted a cheap Product Red one) and not even 2 days later the replacement battery expanded. I would call this
New 580mah Li-on Battery for Apple iPod Nano 2nd Generation – Elite Obsolete Electronics